Though having excellent heat resistance, urea grease is sometimes inferior in acoustic characteristics depending on amine(s) to be used. Accordingly, different greases have been typically used depending on the usage. However, in some applications (e.g. ball bearings installed in a small-sized motor for a household electrical appliance), both of the acoustic characteristics and heat resistance have been required to be satisfied.
In view of the above demand, a diurea grease containing a first amine component including an amine with a cyclohexyl group and a cyclohexyl derivative group having 7 to 12 carbon atoms, and a second amine with an alkyl group having 6 to 22 carbon atoms, the first amine and the second amine being used at a predetermined ratio, has been proposed (see Patent Literature 1).